The present invention relates to a four wheel steer vehicle having steerable front wheels and steerable rear wheels, and more specifically to a rear wheel steer angle control system for preventing a rear end of such a four wheel steer vehicle from swinging outwardly during a turn and for reducing almost to zero a difference between the radii of turning arcs of the outside or inside front and rear wheels.
Japanese patent provisional publication No. 58-97566 discloses one example of a four wheel steer system. This system is arranged to steer the rear wheels in a direction opposite to the steering direction of the front wheels to decrease the turning radius when a steering wheel angle is larger than a predetermined value.
However, this system causes the rear end of the vehicle to swing so outwardly during a turn that the rear end is liable to bump laterally against an object lying alongside the vehicle.